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Overview
| Comment: | First attempt at reducing mutex contention in the unix VFS by providing a separate mutex for each unixInodeInfo object. |
|---|---|
| Downloads: | Tarball | ZIP archive | SQL archive |
| Timelines: | family | ancestors | descendants | both | separate-lock-mutex |
| Files: | files | file ages | folders |
| SHA3-256: | f69afaf00a659cd768a863c5f4a1d527 |
| User & Date: | drh 2018-07-23 21:10:37 |
Context
|
2018-07-23
| ||
| 22:55 | Return an SQLITE_NOMEM error if the locking mutex fails to allocate. Closed-Leaf check-in: 1c948348 user: drh tags: separate-lock-mutex | |
| 21:10 | First attempt at reducing mutex contention in the unix VFS by providing a separate mutex for each unixInodeInfo object. check-in: f69afaf0 user: drh tags: separate-lock-mutex | |
| 18:53 | Fix typo of 'SQLITE_OMIT_WINDOWFUNC'. check-in: 8607b84a user: mistachkin tags: trunk | |
Changes
Changes to src/os_unix.c.
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** An instance of the following structure is allocated for each open
** inode. Or, on LinuxThreads, there is one of these structures for
** each inode opened by each thread.
**
** A single inode can have multiple file descriptors, so each unixFile
** structure contains a pointer to an instance of this object and this
** object keeps a count of the number of unixFile pointing to it.
*/
struct unixInodeInfo {
struct unixFileId fileId; /* The lookup key */
int nShared; /* Number of SHARED locks held */
unsigned char eFileLock; /* One of SHARED_LOCK, RESERVED_LOCK etc. */
unsigned char bProcessLock; /* An exclusive process lock is held */
int nRef; /* Number of pointers to this structure */
unixShmNode *pShmNode; /* Shared memory associated with this inode */
int nLock; /* Number of outstanding file locks */
UnixUnusedFd *pUnused; /* Unused file descriptors to close */
unixInodeInfo *pNext; /* List of all unixInodeInfo objects */
unixInodeInfo *pPrev; /* .... doubly linked */
#if SQLITE_ENABLE_LOCKING_STYLE
unsigned long long sharedByte; /* for AFP simulated shared lock */
#endif
#if OS_VXWORKS
................................................................................
assert( inodeList==pInode );
inodeList = pInode->pNext;
}
if( pInode->pNext ){
assert( pInode->pNext->pPrev==pInode );
pInode->pNext->pPrev = pInode->pPrev;
}
sqlite3_free(pInode);
}
}
assert( inodeList!=0 || nUnusedFd==0 );
}
/*
................................................................................
if( pInode==0 ){
pInode = sqlite3_malloc64( sizeof(*pInode) );
if( pInode==0 ){
return SQLITE_NOMEM_BKPT;
}
memset(pInode, 0, sizeof(*pInode));
memcpy(&pInode->fileId, &fileId, sizeof(fileId));
pInode->nRef = 1;
pInode->pNext = inodeList;
pInode->pPrev = 0;
if( inodeList ) inodeList->pPrev = pInode;
inodeList = pInode;
}else{
pInode->nRef++;
................................................................................
int reserved = 0;
unixFile *pFile = (unixFile*)id;
SimulateIOError( return SQLITE_IOERR_CHECKRESERVEDLOCK; );
assert( pFile );
assert( pFile->eFileLock<=SHARED_LOCK );
unixEnterMutex(); /* Because pFile->pInode is shared across threads */
/* Check if a thread in this process holds such a lock */
if( pFile->pInode->eFileLock>SHARED_LOCK ){
reserved = 1;
}
/* Otherwise see if some other process holds it.
................................................................................
storeLastErrno(pFile, errno);
} else if( lock.l_type!=F_UNLCK ){
reserved = 1;
}
}
#endif
unixLeaveMutex();
OSTRACE(("TEST WR-LOCK %d %d %d (unix)\n", pFile->h, rc, reserved));
*pResOut = reserved;
return rc;
}
/*
................................................................................
**
** Zero is returned if the call completes successfully, or -1 if a call
** to fcntl() fails. In this case, errno is set appropriately (by fcntl()).
*/
static int unixFileLock(unixFile *pFile, struct flock *pLock){
int rc;
unixInodeInfo *pInode = pFile->pInode;
assert( unixMutexHeld() );
assert( pInode!=0 );
if( (pFile->ctrlFlags & (UNIXFILE_EXCL|UNIXFILE_RDONLY))==UNIXFILE_EXCL ){
if( pInode->bProcessLock==0 ){
struct flock lock;
assert( pInode->nLock==0 );
lock.l_whence = SEEK_SET;
lock.l_start = SHARED_FIRST;
lock.l_len = SHARED_SIZE;
................................................................................
*/
assert( pFile->eFileLock!=NO_LOCK || eFileLock==SHARED_LOCK );
assert( eFileLock!=PENDING_LOCK );
assert( eFileLock!=RESERVED_LOCK || pFile->eFileLock==SHARED_LOCK );
/* This mutex is needed because pFile->pInode is shared across threads
*/
unixEnterMutex();
pInode = pFile->pInode;
/* If some thread using this PID has a lock via a different unixFile*
** handle that precludes the requested lock, return BUSY.
*/
if( (pFile->eFileLock!=pInode->eFileLock &&
(pInode->eFileLock>=PENDING_LOCK || eFileLock>SHARED_LOCK))
){
................................................................................
pInode->eFileLock = eFileLock;
}else if( eFileLock==EXCLUSIVE_LOCK ){
pFile->eFileLock = PENDING_LOCK;
pInode->eFileLock = PENDING_LOCK;
}
end_lock:
unixLeaveMutex();
OSTRACE(("LOCK %d %s %s (unix)\n", pFile->h, azFileLock(eFileLock),
rc==SQLITE_OK ? "ok" : "failed"));
return rc;
}
/*
** Add the file descriptor used by file handle pFile to the corresponding
................................................................................
pFile->eFileLock, pFile->pInode->eFileLock, pFile->pInode->nShared,
osGetpid(0)));
assert( eFileLock<=SHARED_LOCK );
if( pFile->eFileLock<=eFileLock ){
return SQLITE_OK;
}
unixEnterMutex();
pInode = pFile->pInode;
assert( pInode->nShared!=0 );
if( pFile->eFileLock>SHARED_LOCK ){
assert( pInode->eFileLock==pFile->eFileLock );
#ifdef SQLITE_DEBUG
/* When reducing a lock such that other processes can start
** reading the database file again, make sure that the
................................................................................
assert( pInode->nLock>=0 );
if( pInode->nLock==0 ){
closePendingFds(pFile);
}
}
end_unlock:
unixLeaveMutex();
if( rc==SQLITE_OK ) pFile->eFileLock = eFileLock;
return rc;
}
/*
** Lower the locking level on file descriptor pFile to eFileLock. eFileLock
** must be either NO_LOCK or SHARED_LOCK.
................................................................................
assert( pFile );
context = (afpLockingContext *) pFile->lockingContext;
if( context->reserved ){
*pResOut = 1;
return SQLITE_OK;
}
unixEnterMutex(); /* Because pFile->pInode is shared across threads */
/* Check if a thread in this process holds such a lock */
if( pFile->pInode->eFileLock>SHARED_LOCK ){
reserved = 1;
}
/* Otherwise see if some other process holds it.
*/
................................................................................
reserved = 1;
}
if( IS_LOCK_ERROR(lrc) ){
rc=lrc;
}
}
unixLeaveMutex();
OSTRACE(("TEST WR-LOCK %d %d %d (afp)\n", pFile->h, rc, reserved));
*pResOut = reserved;
return rc;
}
/*
................................................................................
*/
assert( pFile->eFileLock!=NO_LOCK || eFileLock==SHARED_LOCK );
assert( eFileLock!=PENDING_LOCK );
assert( eFileLock!=RESERVED_LOCK || pFile->eFileLock==SHARED_LOCK );
/* This mutex is needed because pFile->pInode is shared across threads
*/
unixEnterMutex();
pInode = pFile->pInode;
/* If some thread using this PID has a lock via a different unixFile*
** handle that precludes the requested lock, return BUSY.
*/
if( (pFile->eFileLock!=pInode->eFileLock &&
(pInode->eFileLock>=PENDING_LOCK || eFileLock>SHARED_LOCK))
){
................................................................................
pInode->eFileLock = eFileLock;
}else if( eFileLock==EXCLUSIVE_LOCK ){
pFile->eFileLock = PENDING_LOCK;
pInode->eFileLock = PENDING_LOCK;
}
afp_end_lock:
unixLeaveMutex();
OSTRACE(("LOCK %d %s %s (afp)\n", pFile->h, azFileLock(eFileLock),
rc==SQLITE_OK ? "ok" : "failed"));
return rc;
}
/*
** Lower the locking level on file descriptor pFile to eFileLock. eFileLock
................................................................................
pFile->eFileLock, pFile->pInode->eFileLock, pFile->pInode->nShared,
osGetpid(0)));
assert( eFileLock<=SHARED_LOCK );
if( pFile->eFileLock<=eFileLock ){
return SQLITE_OK;
}
unixEnterMutex();
pInode = pFile->pInode;
assert( pInode->nShared!=0 );
if( pFile->eFileLock>SHARED_LOCK ){
assert( pInode->eFileLock==pFile->eFileLock );
SimulateIOErrorBenign(1);
SimulateIOError( h=(-1) )
SimulateIOErrorBenign(0);
................................................................................
assert( pInode->nLock>=0 );
if( pInode->nLock==0 ){
closePendingFds(pFile);
}
}
}
unixLeaveMutex();
if( rc==SQLITE_OK ) pFile->eFileLock = eFileLock;
return rc;
}
/*
** Close a file & cleanup AFP specific locking context
*/
|
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** An instance of the following structure is allocated for each open ** inode. Or, on LinuxThreads, there is one of these structures for ** each inode opened by each thread. ** ** A single inode can have multiple file descriptors, so each unixFile ** structure contains a pointer to an instance of this object and this ** object keeps a count of the number of unixFile pointing to it. ** ** Mutex rules: ** ** (1) The pLockMutex mutex must be held in order to read or write ** any of the locking fields: ** nShared, nLock, eFileLock, or bProcessLock ** ** (2) When nRef>0, then the following fields are unchanging and can ** be read (but not written) without holding any mutex: ** fileId, pLockMutex ** ** (3) With the exceptions above, all the fields may only be read ** or written while holding the global unixBigLock mutex. */ struct unixInodeInfo { struct unixFileId fileId; /* The lookup key */ sqlite3_mutex *pLockMutex; /* Hold this mutex for... */ int nShared; /* Number of SHARED locks held */ int nLock; /* Number of outstanding file locks */ unsigned char eFileLock; /* One of SHARED_LOCK, RESERVED_LOCK etc. */ unsigned char bProcessLock; /* An exclusive process lock is held */ int nRef; /* Number of pointers to this structure */ unixShmNode *pShmNode; /* Shared memory associated with this inode */ UnixUnusedFd *pUnused; /* Unused file descriptors to close */ unixInodeInfo *pNext; /* List of all unixInodeInfo objects */ unixInodeInfo *pPrev; /* .... doubly linked */ #if SQLITE_ENABLE_LOCKING_STYLE unsigned long long sharedByte; /* for AFP simulated shared lock */ #endif #if OS_VXWORKS ................................................................................ assert( inodeList==pInode ); inodeList = pInode->pNext; } if( pInode->pNext ){ assert( pInode->pNext->pPrev==pInode ); pInode->pNext->pPrev = pInode->pPrev; } sqlite3_mutex_free(pInode->pLockMutex); sqlite3_free(pInode); } } assert( inodeList!=0 || nUnusedFd==0 ); } /* ................................................................................ if( pInode==0 ){ pInode = sqlite3_malloc64( sizeof(*pInode) ); if( pInode==0 ){ return SQLITE_NOMEM_BKPT; } memset(pInode, 0, sizeof(*pInode)); memcpy(&pInode->fileId, &fileId, sizeof(fileId)); pInode->pLockMutex = sqlite3_mutex_alloc(SQLITE_MUTEX_FAST); pInode->nRef = 1; pInode->pNext = inodeList; pInode->pPrev = 0; if( inodeList ) inodeList->pPrev = pInode; inodeList = pInode; }else{ pInode->nRef++; ................................................................................ int reserved = 0; unixFile *pFile = (unixFile*)id; SimulateIOError( return SQLITE_IOERR_CHECKRESERVEDLOCK; ); assert( pFile ); assert( pFile->eFileLock<=SHARED_LOCK ); sqlite3_mutex_enter(pFile->pInode->pLockMutex); /* Check if a thread in this process holds such a lock */ if( pFile->pInode->eFileLock>SHARED_LOCK ){ reserved = 1; } /* Otherwise see if some other process holds it. ................................................................................ storeLastErrno(pFile, errno); } else if( lock.l_type!=F_UNLCK ){ reserved = 1; } } #endif sqlite3_mutex_leave(pFile->pInode->pLockMutex); OSTRACE(("TEST WR-LOCK %d %d %d (unix)\n", pFile->h, rc, reserved)); *pResOut = reserved; return rc; } /* ................................................................................ ** ** Zero is returned if the call completes successfully, or -1 if a call ** to fcntl() fails. In this case, errno is set appropriately (by fcntl()). */ static int unixFileLock(unixFile *pFile, struct flock *pLock){ int rc; unixInodeInfo *pInode = pFile->pInode; assert( pInode!=0 ); assert( sqlite3_mutex_held(pInode->pLockMutex) ); if( (pFile->ctrlFlags & (UNIXFILE_EXCL|UNIXFILE_RDONLY))==UNIXFILE_EXCL ){ if( pInode->bProcessLock==0 ){ struct flock lock; assert( pInode->nLock==0 ); lock.l_whence = SEEK_SET; lock.l_start = SHARED_FIRST; lock.l_len = SHARED_SIZE; ................................................................................ */ assert( pFile->eFileLock!=NO_LOCK || eFileLock==SHARED_LOCK ); assert( eFileLock!=PENDING_LOCK ); assert( eFileLock!=RESERVED_LOCK || pFile->eFileLock==SHARED_LOCK ); /* This mutex is needed because pFile->pInode is shared across threads */ pInode = pFile->pInode; sqlite3_mutex_enter(pInode->pLockMutex); /* If some thread using this PID has a lock via a different unixFile* ** handle that precludes the requested lock, return BUSY. */ if( (pFile->eFileLock!=pInode->eFileLock && (pInode->eFileLock>=PENDING_LOCK || eFileLock>SHARED_LOCK)) ){ ................................................................................ pInode->eFileLock = eFileLock; }else if( eFileLock==EXCLUSIVE_LOCK ){ pFile->eFileLock = PENDING_LOCK; pInode->eFileLock = PENDING_LOCK; } end_lock: sqlite3_mutex_leave(pInode->pLockMutex); OSTRACE(("LOCK %d %s %s (unix)\n", pFile->h, azFileLock(eFileLock), rc==SQLITE_OK ? "ok" : "failed")); return rc; } /* ** Add the file descriptor used by file handle pFile to the corresponding ................................................................................ pFile->eFileLock, pFile->pInode->eFileLock, pFile->pInode->nShared, osGetpid(0))); assert( eFileLock<=SHARED_LOCK ); if( pFile->eFileLock<=eFileLock ){ return SQLITE_OK; } pInode = pFile->pInode; sqlite3_mutex_enter(pInode->pLockMutex); assert( pInode->nShared!=0 ); if( pFile->eFileLock>SHARED_LOCK ){ assert( pInode->eFileLock==pFile->eFileLock ); #ifdef SQLITE_DEBUG /* When reducing a lock such that other processes can start ** reading the database file again, make sure that the ................................................................................ assert( pInode->nLock>=0 ); if( pInode->nLock==0 ){ closePendingFds(pFile); } } end_unlock: sqlite3_mutex_leave(pInode->pLockMutex); if( rc==SQLITE_OK ) pFile->eFileLock = eFileLock; return rc; } /* ** Lower the locking level on file descriptor pFile to eFileLock. eFileLock ** must be either NO_LOCK or SHARED_LOCK. ................................................................................ assert( pFile ); context = (afpLockingContext *) pFile->lockingContext; if( context->reserved ){ *pResOut = 1; return SQLITE_OK; } sqlite3_mutex_enter(pFile->pInode->pLockMutex); /* Check if a thread in this process holds such a lock */ if( pFile->pInode->eFileLock>SHARED_LOCK ){ reserved = 1; } /* Otherwise see if some other process holds it. */ ................................................................................ reserved = 1; } if( IS_LOCK_ERROR(lrc) ){ rc=lrc; } } sqlite3_mutex_leave(pFile->pInode->pLockMutex); OSTRACE(("TEST WR-LOCK %d %d %d (afp)\n", pFile->h, rc, reserved)); *pResOut = reserved; return rc; } /* ................................................................................ */ assert( pFile->eFileLock!=NO_LOCK || eFileLock==SHARED_LOCK ); assert( eFileLock!=PENDING_LOCK ); assert( eFileLock!=RESERVED_LOCK || pFile->eFileLock==SHARED_LOCK ); /* This mutex is needed because pFile->pInode is shared across threads */ pInode = pFile->pInode; sqlite3_mutex_enter(pInode->pLockMutex); /* If some thread using this PID has a lock via a different unixFile* ** handle that precludes the requested lock, return BUSY. */ if( (pFile->eFileLock!=pInode->eFileLock && (pInode->eFileLock>=PENDING_LOCK || eFileLock>SHARED_LOCK)) ){ ................................................................................ pInode->eFileLock = eFileLock; }else if( eFileLock==EXCLUSIVE_LOCK ){ pFile->eFileLock = PENDING_LOCK; pInode->eFileLock = PENDING_LOCK; } afp_end_lock: sqlite3_mutex_leave(pInode->pLockMutex); OSTRACE(("LOCK %d %s %s (afp)\n", pFile->h, azFileLock(eFileLock), rc==SQLITE_OK ? "ok" : "failed")); return rc; } /* ** Lower the locking level on file descriptor pFile to eFileLock. eFileLock ................................................................................ pFile->eFileLock, pFile->pInode->eFileLock, pFile->pInode->nShared, osGetpid(0))); assert( eFileLock<=SHARED_LOCK ); if( pFile->eFileLock<=eFileLock ){ return SQLITE_OK; } pInode = pFile->pInode; sqlite3_mutex_enter(pInode->pLockMutex); assert( pInode->nShared!=0 ); if( pFile->eFileLock>SHARED_LOCK ){ assert( pInode->eFileLock==pFile->eFileLock ); SimulateIOErrorBenign(1); SimulateIOError( h=(-1) ) SimulateIOErrorBenign(0); ................................................................................ assert( pInode->nLock>=0 ); if( pInode->nLock==0 ){ closePendingFds(pFile); } } } sqlite3_mutex_leave(pInode->pLockMutex); if( rc==SQLITE_OK ) pFile->eFileLock = eFileLock; return rc; } /* ** Close a file & cleanup AFP specific locking context */ |